Reticle compartment and diffusor plate

ABSTRACT

A reticle compartment defining an enclosed interior adapted to store at least two reticles in a reticle storage portion, including an inlet port, through which a purge gas can enter the enclosed interior, and an outlet port, through which the purge gas can exit the enclosed interior, wherein the reticle compartment further includes a first diffusor plate arranged in the enclosed interior between the inlet port and the reticle storage portion, wherein the first diffusor plate is provided with openings, through which the purge gas can flow, the openings in a central section of the first diffusor plate being provided with a larger individual opening area and/or providing a larger total opening area per unit area than openings in a peripheral section of the first diffusor plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/EP2017/071631, having an International Filing Date of 29 Aug. 2017,which designated the United States of America, and which InternationalApplication was published under PCT Article 21(2) as WO Publication No.2018/041816 A1, and which claims priority from, and the benefit of,European Application No. 16186441.8, filed 30 Aug. 2016, the disclosuresof which are incorporated herein by reference in their entireties.

BACKGROUND 1. Field

The present disclosure relates to a reticle compartment and a diffusorplate adapted to be used in an interior of a reticle compartment.

2. Brief Description of Related Developments

In semiconductor technology, reticles or photomasks are used for themass production of integrated circuit devices. A reticle is an opaqueplate with holes or transparencies that allow light to shine through ina defined pattern.

It is well known that any type of contamination, for example dustparticles or organic materials adhering to a reticle can causedegradation of the quality of a projected pattern. It is thus of utmostimportance to store and handle reticles in an absolutely cleanenvironment.

It is known to store reticles in so called compartment stockers, whichcan store up to a few thousand individual reticles. Reticles within suchstockers are, for example, stored in designated reticle compartments,which are designed to hold a number of reticles, for example 1, 2, 4, 6,8 or 10.

From U.S. Pat. No. 8,403,143 B2 a reticle storing compartment is known.This compartment is designed for the storage of one reticle. In order toreduce the number of potentially contaminating particles within thecompartment, two methods are disclosed in this document, i.e. fillingthe reticle compartment with a clean gas by means of a purging head,and, alternatively, exhausting the gas in the compartment by means of avacuum pump.

Purging advantageously comprises a constant flow of clean gas throughthe compartment, the gas entering by an inlet port, and exiting by anoutlet port of the compartment.

Typical purging gases are, for example, extremely clean dry air andnitrogen. Providing such gases is a cost factor, so that a reduction ofthe amount of gas flowing through a reticle compartment, which is at thesame time sufficient for an effective purge, would be advantageous.

This aspect becomes even more significant in case of reticlecompartments adapted to store a multitude of reticles. In case of priorart purge gas inlet and outlet, pronounced turbulences of purge gasflowing through the compartment occur, leading to the necessity of ahigher throughput of purge gas.

SUMMARY

The present disclosure attempts to provide a reticle compartment adaptedfor purge cleaning of reticles stored therein, for which the throughputof purge gas is minimized.

This aim is achieved with a reticle compartment comprising the featuresof claim 1 and a diffusor plate comprising the features of claim 12.Advantageous aspects of the reticle compartment according to the presentdisclosure are the subject matter of the dependent claims.

The reticle compartment according to the present disclosure ensures amore uniform and less turbulent flow of purge gas through its enclosedinterior, in which the multitude of reticles are stored. This isespecially achieved by the design of the diffusor plate arranged betweenthe inlet port and the portion of the reticle interior where thereticles are stored. Providing the diffusor plate with openings withlarger individual opening areas in its central section as compared to aperipheral section, and/or such that the openings in the central sectionprovide a larger total opening area per unit area than openings in theperipheral area establishes a substantially more uniform flow comparedto prior art diffusor plates designed for example with a uniform openingsize over the whole diffusor plate area. This diffusor plate designaccording to the present disclosure also significantly reducesturbulences within the compartment.

Advantageously, the opening areas of individual openings becomeprogressively smaller from the central section to at least oneperipheral section of the diffuser plate. Alternatively or in additionhereto, the total opening area per unit area can become progressivelysmaller from the central section to least one peripheral section of thediffuser plate by means of decreasing the number of openings per unitarea. For example, in the central section, there can be provided 4openings per suitably defined unit area, and in a peripheral sectionthere can be provided 3, 2, or 1 opening(s) per unit area. The decreaseof individual opening area and total opening area per unit area from thecentral section to a peripheral section can be combined. For example, inthe central area there can be provided 4 openings per unit area with afirst individual opening area, and in a peripheral section there can beprovided 3, 2, or 1 opening(s) per unit area with a second individualopening area, the second individual opening area being smaller than thefirst individual opening area.

According to an advantageous embodiment of the reticle compartment,there is provided a second diffusor plate arranged between the reticlestorage portion and the outlet port of the reticle compartment.Providing such a second diffusor plate on the outlet side of the reticlecompartment further enhances the uniformity of flow and reducesturbulences. Advantageously, both diffusor plates extend parallel.

Advantageously, the second diffusor plate is designed essentially likethe first diffusor plate, i.e. comprising openings in a central sectionprovided with a larger individual opening area than openings inperipheral sections. Also, the number of openings per unit area can bemodified, as described above. By designing both diffusor plates in thesame manner, especially with the positions and opening areas or sizes ofthe respective openings aligned to one another, uniformity of flow of apurge gas can be further enhanced, as well as turbulences reduced.Alternatively, it is possible to provide the second diffusor plate witha different design compared to the first diffusor plate. For example,the second diffusor plate can comprise a different arrangement ofindividual openings and/or individual openings comprising differentindividual opening areas and/or different total opening areas per unitarea in at least one section as compared to the first diffusor plate.

Advantageously, the reticle storage portion is provided to store thereticles such that each reticle extends essentially perpendicularly tothe first diffusor plate and/or the second diffusor plate. Thisorthogonal arrangement of stored reticles relative to the diffusorplate(s) ensures the uniform and smooth flow of purge gas along each ofthe stored reticles, the uniform flow especially ensuring that minimalamounts of purge gas are sufficient to guarantee an optimal purgingeffect.

According to a preferred aspect of the present disclosure, the reticlecompartment is made, at least in part, of at least one metal material.By this choice of material the release of gases (outgassing) that aredissolved, trapped or absorbed in the material of the reticlecompartment can be minimized. In prior art reticle compartments, themain materials used for manufacture were plastic materials, in whichoutgassing effects are significantly more pronounced. Preferred metalmaterials are aluminium and/or stainless steel. Advantageously, a bodymember and a lid of a reticle compartment can be made of aluminium,whereas diffusor plates are made of stainless steel.

Expediently, the reticle compartment according to the present disclosurecomprises retainer elements, especially slots or ridges, on or betweenwhich reticles can be positioned. By providing an expedient amount ofsuch retainer elements, reticle compartments can be specifically adaptedto store a desired number of reticles.

Advantageously, the retainer elements are provided with inserts and/orlinings made of a polymer material such as, for example, a thermoplasticmaterial or a composite thereof. As such inserts and/or linings have asmaller volume and/or surface area compared to the reticle compartmentas a whole, outgassing effects due to such inserts and/or linings arereduced. Suitable polymer materials include, but are not limited to,polybenzimidazole (PBI), polyimide (PI), polyamide-imide (PAI),polytetrafluoroethylene (PTFE), polychlorotetrafluoroethylene (PCTFE),polyetheretherketone (PEEK), polyethylene terephthalate (PET-P),polycarbonate (PC), acetal, and composites (e.g., glass and/or carbonfiber composites) and combinations thereof. In some aspects, the polymermaterial is chosen to have relatively low outgassing effects as comparedto other polymer materials.

The reticle compartment according to the present disclosure isadvantageously adapted to efficiently store a multitude of reticles in aclean environment, wherein especially 2, 3, 4, 5, 6, 7, 8, 9, 10 or morereticles can be stored.

According to a preferred aspect, the openings of the first diffusorplate and/or the openings of the second diffusor plate are provided withat least two, especially 2, 3, 4, 5 or 6 different individual openingareas, the opening areas decreasing from a largest individual openingarea in a central section of the first and/or second diffusor plates toa smallest individual opening area in the vicinity of the peripheralsection or edges of the first and/or second diffusor plates. Thisespecially means that the openings in the peripheral section or edgesections of the first and/or second diffusor plates, i.e. the mostperipheral sections, are provided with the smallest opening areas, theopening areas of the openings increasing towards the central sections ofthe first and/or second diffusor plates. For example, the openings in acentral section can be provided with first opening areas, for exampleeach greater than about 15 mm2 and openings in the vicinity of theedges, i.e. in the peripheral section, of the first and/or seconddiffusor plates with second opening areas each less than about 15 mm2.In some aspects, openings in an intermediate section, i.e. between thecentral section and the peripheral section of the first and/or seconddiffusor plates, can be provided with third opening areas which areintermediate the areas of the first and second opening areas. Forexample, in some aspects the first opening areas are each about 19 to 22mm2, the second opening areas are each about 11 to 14 mm2, and the thirdopening areas are each about 15 to about 18 mm2. In some aspects, thetotal opening area of a central section is greater than about 450 mm2and the total opening area of a peripheral section is less than about450 mm2. For example, the total opening area of a central section can beabout 500 to 600 mm2, the total opening area of an intermediate area canbe about 400 to 500 mm2, and the total opening areas of a peripheralsection can be about 300 to 400 mm2.

According to a preferred aspect, all of the outermost peripheralopenings of the first and/or second diffusor plates are smaller in theirindividual opening area than openings in the central section.

Expediently, the individual openings comprise opening areas which areround and/or oval and/or square and/or triangular and/or oblong and/oregg shaped and/or crescent shaped and/or slit shaped and/or polygonshaped.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred aspects of the present disclosure will now be furtherdescribed with reference to the appended figures.

FIG. 1 shows a schematically simplified side sectional view of a firstaspect of a reticle compartment according to the present disclosure,

FIG. 2 shows a plan view of a preferred aspect of a diffusor plateaccording to the present disclosure,

FIG. 3 shows a perspective view of a preferred aspect of body member ofa reticle compartment according to the present disclosure,

FIG. 4 shows a preferred aspect of a lid of a reticle compartmentaccording the present disclosure, which, together with the bodyaccording to FIG. 3, forms a reticle compartment, and

FIGS. 5a-5i show plan views of various further preferred aspects ofdiffusor plates according to the present disclosure.

DETAILED DESCRIPTION

FIG. 1 shows, in schematic simplification, a preferred aspect of areticle compartment according to the present disclosure, generallydesignated 10.

It defines a closed interior 12, comprising a reticle storage portion14, in which a multitude of reticles 22 can be stored. The actualinteraction between the reticles and the compartment is not shown inFIG. 1. Especially, no retainer elements for holding individual reticlesare shown.

The reticle compartment comprises an inlet port 16, through which apurge gas (indicated by arrow 16′) can enter the enclosed interior 12 ofthe reticle compartment. It further comprises an outlet port 18, throughwhich purge gas can exit the enclosed interior 12, indicated by means ofarrow 18′.

To ensure a uniform and essentially turbulence-free flow of purge gasthrough the whole volume of the reticle storage portion 14, a firstdiffusor plate 12 is arranged between inlet port 16 and reticle storageportion 14. The first diffusor plate 24 comprises a multitude ofopenings 25, through which purge gas can enter the reticle storageportion 14. As schematically indicated in FIG. 1, and especially can beseen in FIG. 2, the openings 25 a in a central section of first diffusorplate 24 are larger, i.e. are provided with a larger opening area or alarger diameter than openings 25 b in peripheral sections.

Between reticle storage portion 14 and outlet port 18, there is provideda second diffusor plate 26, which is also provided with openings 27 aand 27 b. Advantageously, the pattern of openings 27 a and 27 bcorresponds to that of first diffusor plate 24, i.e. openings 27 a inthe central section have a larger opening area than openings 27 b inperipheral sections.

As can further be seen in FIG. 1, the reticles 22 stored in reticlestorage portion 14 are arranged orthogonally relatively to the first andsecond diffusor plate 24, 26. This arrangement ensures that purge gasflowing through the reticle compartment from inlet port 16 to outletport 18 provides a uniform flow, so that all reticles 22 are essentiallyequally exposed to purge gas and thereby purged in an optimal manner.This uniform flow is especially enhanced by the pattern of openings 25a, 25 b, 27 a, 27 b which ensures that the flow of purge gas along moreperipherally arranged reticles (for example reticle 22 b as indicated inFIG. 1) essentially corresponds to that along a more central reticle(for example reticle 22 a as indicated in FIG. 1).

Typically, a reticle compartment comprises a body member provided withretainer elements for holding individual reticles and a lid adapted toclose the volume defined by the body member. Preferred aspects of such abody member and a lid are shown in FIGS. 3 and 4 respectively. Be itnoted that identical or similar components as already described withreference to FIGS. 1 and 2 have the same reference numerals in FIGS. 3and 4.

FIG. 3 shows a body member 10 a. Body member 10 a comprises a pluralityof retainer elements 11 on opposing inner walls of body member 10 a. Theretainer elements are adapted to hold individual reticles. To illustratethis, one reticle 22 is shown in FIG. 3, which, with two opposite sides,rests on corresponding retainer elements 11. As can be immediately seen,the retainer elements 11 are adapted for horizontal storage of reticles22. The retainer elements 11 according to the embodiment of FIG. 3 areprovided as ridges.

The body element 10 a is manufactured of a metal material, for examplealuminium or stainless steel.

In order to avoid electrostatic effects between the body member 10 a orthe reticle compartment and reticles 22 stored therein, each retainerelement 11 is provided with inserts 13 made of a polymer material. Thus,a reticle stored within the reticle compartment 10 on retainer elements11 will not contact these retainer elements directly, but will beinsulated from them by means of inserts 13. Inserts 13 can also beprovided on the inside walls of body member 10 a. This electricinsulation further reduces the tendency of reticles to attractcontamination such as dust particles within the reticle compartment.Inserts 13 also serve to prevent scratching of reticles.

As can be seen in FIG. 3, the rear side of body member 10 a is providedwith a diffusor plate 26 and an outlet port (not visible in FIG. 3),analogously to the aspect of FIG. 1. The openings 27 aa in the centralsection of diffusor plate 26 are provided with larger opening areas thanopenings 27 b in peripheral sections.

For ease of handling within a compartment stocker, the body member 10 ais provided with feet 10 b.

A lid 10 c as shown in FIG. 4 is adapted to interact with body member 10a, i.e. to tightly close the volume defined by body member 10 a toprovide an enclosed interior of reticle compartment 10.

Lid 10 c is provided with a locking mechanism 17, adapted to interactwith grooves 19 provided in the outside walls of body member 10 a (seeFIG. 3). The inside edges 41 of the lid and/or the edges 31 at theopening of body member 10 a are provided with seal members, such that byinteraction of the lock mechanism 17 with the groves 19 a gas tightconnection between lid and body member is achieved.

The lid is provided with a diffusor plate 24. An inlet port 16 alsoprovided on lid 10 c is not visible in FIG. 4.

The openings 25 a in the central section of diffusor plate 24 areprovided with larger opening areas than those openings 25 b inperipheral or edge sections, as explained above. Especially, theopenings in the vicinity of at least some of the edges of the diffusorplates are provided with the smallest opening areas. In some aspects,only a top and/or bottom edge section of the diffusor plate is providedwith the smallest opening areas. In other aspects, all of the edgesections of the diffusor plate are provided with the smallest openingareas.

The lid 10 c is manufactured of a metallic material, for examplealuminium and/or stainless steel.

The diffusor plates 24, 26 are preferably made of stainless steel.However, aluminium can also be used.

As explained with reference to FIG. 3, the reticle compartment shown isadapted for horizontal storage of reticles.

Advantageously, the reticles are stored orthogonally in relation to thediffusor plates. A vertical storage within a reticle compartment wouldalso be possible. In this case, the retainer elements are advantageouslyprovided as grooves, to ensure safe positioning and handling.

The reticle container 10 comprising body element 10 a and lid 10 c isadapted to store reticles within a reticle stocker. In order to insertor extract a reticle, lid 10 c is removed from the body member.

Under normal storage conditions within a reticle stocker, the inlet port16 is connected to a pressurized purge gas source. After flowing throughthe reticle compartment in the manner described above, purge gas isexhausted into the reticle stocker, from where it is drawn out of thereticle stocker by a vacuum device.

In FIGS. 5a-5i , further designs for preferred aspects of diffusorplates according to the present disclosure are shown. The diffusorplates shown in FIG. 5 can either be used as first and/or seconddiffusor plate as specified above. It is also possible to utilizedifferent ones of these diffusor plate designs as first and seconddiffusor plate respectively. The design according to FIG. 5a comprisesessentially square openings 50 in a central sections, and slit-shapedopenings 52 in peripheral sections. In this aspect, the square shapedopenings 50 provide a larger total opening area per unit area thanslit-shaped openings 52. An expediently size unit area is, as anexample, designated 80 in FIG. 5a . Such unit areas are not shown in thefurther aspects of FIGS. 5a -5 i.

According to the aspect of FIG. 5b , triangular openings 54 areprovided. The bases of these triangular openings 54 are located in thecentral section of the diffusor plate, and the tips towards the upperand lower peripheral sections. Again, comparing the central section tothe upper and lower peripheral sections, the total opening area per unitarea is larger in the central section.

According to the aspect of FIG. 5c , larger square shaped openings 56are provided in the central section of the diffusor plate, and smallersquare shaped openings 58 in the peripheral section. Again, the totalopening area per unit area is larger in the central section.

According to the aspect of FIG. 5d , a number of oblong or rectangularopenings 58 are provided. The openings in the central section are largerthan those in the left and right peripheral sections, the opening areasthus decreasing from the central section to these peripheral sections.

The aspect of the diffusor plate according to FIG. 5e has similaritiesto the aspect of FIG. 5c . However, here all square shaped openings 60have the same opening area. However, the density of openings is largerin the central section than in the peripheral section. Thus, the centralsection has a larger total opening per unit area as compared to theperipheral section.

According to the aspect of FIG. 5f , oblong or rectangular shapedopenings 62 are provided, the opening area of which decreases towardsthe left and right peripheral sections of the diffusor plate.

According to the aspect of FIG. 5g , a number of oval shaped openings 64are provided. The oval shaped opening 64 in the central section havelarger opening areas as compared to openings in the left and rightperipheral sections.

According to the aspect of FIG. 5h , a number of triangular shapedopenings 66, 68 are provided. Here again, similarly to FIG. 5b , thebases of the triangular shaped openings are located in the centralsection, and the tips of the openings in the peripheral sections of thediffusor plate. Thus, the total opening area per unit area is larger inthe central section than in the peripheral sections.

According to the aspect of FIG. 5i , a number of rectangular or oblongopenings 70 are provided, the opening area of which decreases from acentral section towards the left and right as well as top and bottomperipheral sections.

As will be appreciated, and as partly expanded on above, all thesediffusor plate designs are provided with openings with larger individualopening areas and/or providing a larger total opening area per unit areain their central sections as compared to peripheral sections.

What is claimed is:
 1. A reticle compartment defining an enclosedinterior adapted to store at least two reticles in a reticle storageportion, comprising an inlet port, through which a purge gas can enterthe enclosed interior, and an outlet port, through which the purge gascan exit the enclosed interior, wherein the reticle compartment furthercomprises a first diffusor plate arranged in the enclosed interiorbetween the inlet port and the reticle storage portion, wherein thefirst diffusor plate is provided with openings, through which the purgegas can flow, the openings in a central section of the first diffusorplate being provided with a larger individual opening area and/orproviding a larger total opening area per unit area than openings in aperipheral section of the first diffusor plate, wherein the peripheralsection circumscribes the central section.
 2. The reticle compartmentaccording to claim 1, wherein there is provided a second diffusor platearranged between the reticle storage portion and the outlet port.
 3. Thereticle compartment according to claim 2, wherein the second diffusorplate is provided with openings, through which the purge gas can flow,the openings in a central section of the second diffusor plate beingprovided with a larger individual opening area and/or providing a largertotal opening area per unit area than openings in the peripheral sectionof the second diffusor plate.
 4. The reticle compartment according toclaim 3, wherein the openings of the first diffusor plate and/or theopenings of the second diffusor plate are provided with at least 2different individual opening areas, the opening areas decreasing from alargest individual opening area for openings in a central section of thefirst and/or second diffusor plates, to a smallest opening area in thevicinity of the peripheral section of the first and/or second diffusorplates.
 5. The reticle compartment according to claim 2, wherein thereticle storage portion is provided to store the at least two reticlessuch that each reticle extends essentially perpendicularly to the firstdiffusor plate and/or the second diffusor plate.
 6. The reticlecompartment according to claim 1, made at least in part of at least onemetal material, the metal material comprising aluminium and/or stainlesssteel.
 7. The reticle compartment according to claim 1, comprisingretainer elements on or between which reticles can be positioned.
 8. Thereticle compartment according to claim 7, wherein the retainer elementsare provided with inserts and/or linings made of a polymer material. 9.The reticle compartment according to claim 1, wherein all outermostperipheral openings are smaller in their individual opening area thanopenings in the central section.
 10. The reticle compartment accordingto claim 1, wherein the individual openings comprise opening areas whichare round and/or oval and/or square and/or triangular and/or oblongand/or egg shaped and/or crescent shaped and/or slit shaped and/orpolygon shaped.
 11. A diffusor plate adapted to be used in a reticlecompartment according to claim
 1. 12. A diffusor plate adapted to beused in an interior of a reticle compartment between an inlet port ofthe reticle compartment and a reticle storage portion of the reticlecompartment and/or between the reticle storage portion of the reticlecompartment and an outlet port of the reticle compartment, provided withopenings, openings in a central section of the diffusor plate beingprovided with a larger individual opening area and/or providing a largertotal opening area per unit area than openings in a peripheral sectionof the diffusor plate, wherein the peripheral section circumscribes thecentral section.